In the preparation of a polyolefin by polymerization of an olefin, a catalyst is used for efficient olefin polymerization, and specifically, various catalysts such as a Zeigler-Natta catalyst, a chromium-based catalyst, a metallocene catalyst, and the like are used according to the kind of central metals. Since these catalysts have different catalytic activities and the polyolefins prepared using the same have different molecular weight distributions, stereoregularities, and co-monomer reaction properties, the catalysts are selectively used according to each preparation process and applied product.
In general, a catalyst for synthesis of an olefin, called a Zeigler-Natta catalyst, refers to a solid catalyst consisting of a main catalyst that is a main component, a cocatalyst that is an organic metal compound, and an electron donor, it has been widely studied to improve polymerization activity and stereoregularity, and many related technologies have been suggested.
Specifically, WO2003-068828 discloses a method of changing stereoregularity of polypropylene by applying various internal electron donors. However, since a process of synthesizing an internal electron donor is complicated and difficult to commercially apply, it is disadvantageous.
A Zeigler-Natta catalyst directly influences the characteristics and properties of a produced polyolefin according to the components, structure, preparation method, and the like. Thus, in order to change the properties of a produced polyolefin, changes in the components of a catalyst, the structure of a support, and the preparation method of a catalyst and the like should be involved in the preparation of a catalyst. Further, studies on the activity of the catalyst, and the molecular weight and the stereoregularity of the produced polymer, which are changed due to the preparation method or components of each catalyst and the like, should be combined.
Particularly, among polyolefin resins, polypropylene resin has excellent stiffness and chemical resistance and thus is widely used as interior parts for automobiles, components for electric home appliance, and the like. However, when the polypropylene resin is used as interior parts of automobiles or materials of injection molded products for general packaging, it does not have good transparency and thus has inferior formability, and does not have good flexural modulus and heat deflection temperature and thus there are many limitations in using them.
Accordingly, there is an increasing demand for the development of a Zeigler-Nana catalyst for synthesis of polyolefins, which can improve formability such as transparency and heat deflection temperature as well as basic properties such as apparent density and stereoregularity, while maintaining high polymerization activity.